The best way to tell if you are obtaining adequate nutrition is to enter everything you eat into a simple & free program called the CRON-O-Meter. If you scroll down, you will see many posts on it or just search Google.

Using Jack La Lanne as an example is fine & I do not disagree, but it is an isolated single case example and if we accept its valididty then we could also then use George Burns as an acceotable one, and he outlived Jack Le Lanne, smoked, ate a poor diet & never exercised.

As you said, it is important to do enough exercise/ activity to maintain fitness, health, balance, strength, & flexibility into old age and this does not take a lot of time &/or effort.

However, more than that may not provide any additional health benefit & may be counterproductive in the long run.

A recent very well done large study on humans showed that if your were overweight or obese, then being fit lowered your disease risk & increased your chance for longevity. And the "fitter" your were, the better. However, in those who had the lowest BMI, the lowest risk was in those who burned less than 1500 calories in exercise a week. This was the second lowest quintile just over the one representing "no" exercise. Those who burned more than that had higher risks. This is in agreement with many other studies showing that more is not always better.